Pappas–Rapoport flatness conjecture for spin local models at parahoric level

Let F/F0F/F_0 be a quadratic extension, let (V,ϕ)(V,\phi) be a symmetric space of dimension 2n+22n+2, and let I[0,n]I\subset [0,n] be non-empty. Let \RMI±\RM^\pm_I be the spin local model over \COF\CO_F, and let \RMI±\loc\RM^{\pm\loc}_I be the schematic closure of its generic fiber in \RMI±\RM^\pm_I. Pappas–Rapoport's flatness conjecture. The spin local model \RMI±\RM^\pm_I is flat over \COF\CO_F. Equivalently, \RMI±=\RMI±\loc\RM^\pm_I=\RM^{\pm\loc}_I. The paper states that the schematic closure is identified with a Pappas–Zhu local model and has strong geometric properties, but the supplied parser status does not establish that the conjecture itself is resolved.

Sources & referencesView supporting material

Primary source

Jie Yang, Ioannis Zachos and Zhihao Zhao, “On p-adic integral moduli schemes and local models for PEL type D”, arXiv:2602.23813 (2026).

Additional references

2 papers in this index state this conjecture (2025–2026). The statement above is taken from the most recent of them; the others are arXiv:2512.16646.

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